1. Field of the Invention
This invention relates to an endoscope having a bending portion covered with a covering member.
2. Description of the Related Art
The outer periphery of a bending portion of an endoscope is covered with a flexible covering member called a bending rubber. The bending rubber is formed into a relatively thin tubular shape. The end of the bending rubber is externally wound with a thread such that it is fastened and fixed to members such as a bending tube, a distal hard portion and a joint tube. FIG. 15A shows an example in which a distal end portion 102 of a bending rubber (envelope) 101 is wound with a thread such that it is fixed to a distal hard portion. A distal end 104 of the bending rubber 101 contacts a rear end face (contact surface) 106 of a cover 105 of the distal hard portion. The rear end face 106 of the cover 105 of the distal hard portion is an end face perpendicular to the outer peripheral surface of a main body 103 of the distal hard portion (face orthogonal to the central axis of the distal hard portion), and a step is formed by the rear end face 106 of the cover 105 of the distal hard portion and the outer peripheral surface of the main body 103 of the distal hard portion. Further, the distal end (cut end face) 104 of the bending rubber 101 is put into contact with the rear end face 106.
Endoscopes having such attachment structures are also shown in, for example, US 2002/0040179 A1 and US 2005/0209508 A1. In US 2002/0040179 A1 and US 2005/0209508 A1, a portion wound with a thread to be fixed to the outside of the end of a bending rubber is fitted into an annular concave portion formed smaller in diameter than the outermost periphery of a cover in the outer periphery of the cover of a distal hard portion. The distal end face of the bending rubber is placed in collision with an end face perpendicular to the main body of the distal hard portion located on the distal side of the annular concave portion of the cover.
Furthermore, the operation of covering the bending portion and the distal hard portion with the bending rubber is carried out in the order shown in FIGS. 16A to 16D. First, as shown in FIG. 16A, the bending rubber 101 is brought to cover from the bending portion up to the distal hard portion cover 105 of the distal hard portion main body 103. Here, the inside diameter of the bending rubber 101 in a free state is smaller than the outside diameter of the distal hard portion main body 103. Therefore, the bending rubber 101 covers from the outer periphery of the distal hard portion cover 105 to the outer periphery of the distal hard portion main body 103 in a substantially close contact state.
Then, as shown in FIG. 16B, a thread 107 is wound around the outer periphery of the distal end of the bending rubber 101 corresponding to the outer peripheral portion of the distal hard portion main body 103 avoiding the cover 105 of the distal hard portion.
Then, as shown in FIG. 16C, a cutter 108 (e.g., a razor) is put on an extended budging portion located at the step between the rear end of the distal hard portion cover 105 and the distal hard portion main body 103 in the bending rubber 101 fastened by the thread, thereby cutting off an extra portion of the bending rubber 101 covering the outer periphery of the distal hard portion cover 105.
Thus, as shown in FIG. 16D, the distal end of the bending rubber 101 comes into the step, and the distal end 104 of the bending rubber 101 is brought into collision with the rear end face 106 of the cover 105 of the distal hard portion. Subsequently, as shown in FIG. 15A, an adhesive 109 is applied to the outer periphery of a thread-wound portion wound with the thread 107 to fix the thread-wound portion.